82
3.3.3 Basic Format of Transmission Messages
Basically, the BHT-5000 transmits data as a unit of a file. First, it transmits a heading
text which includes the attribute information of a file (e.g., file name and the number of
data texts) to be transmitted. Following the heading text, it transmits the data text in
the file. A heading text and data text comprise a text.
In actual text transmission, the text is divided into several blocks, and a header and
terminator are added to each block. If the serial number management or error
checking by BCC (Block Check Character) is required, the serial number or BCC is also
added to each block, respectively. This procedure forms a transmission block. A set of
transmission blocks makes up one transmission message.
Shown below is an example of a transmission message formed with the BHT-protocol.
S
O
H
E
T
X
B
C
C
S
T
X
E
T
X
B
C
C
S
T
X
E
T
X
B
C
C
Transmission block
Transmission block
Transmission block
Data text 1
Data text 2
Data text n
Heading text
Heading text
Data text 1
Serial
number
Serial
number
Data text n
Transmission
Message
Text
In the above figure, SOH, STX, and ETX are text control characters as described in
Subsection 3.3.2. The serial number is added to every data text in order to identify
those texts. For BCC, refer to Subsection 3.3.6.
